In the last 30 days

• Open/close A spacetime cloak, or a history editor

  Martin W McCall et al 2011 J. Opt. 13 024003 Tag this article

  Article References Full text PDF (484 KB)

  We introduce a new type of electromagnetic cloak, the spacetime cloak (STC), which conceals events rather than objects. Non-emitting events occurring during a restricted period are never suspected by a distant observer. The cloak works by locally manipulating the speed of light of an initially uniform light distribution, whilst the light rays themselves always follow straight paths. Any 'perfect' spacetime cloak would necessarily rely upon the technology of electromagnetic metamaterials, which has already been shown to be capable of deforming light in ways hitherto unforeseen—to produce, for example, an electromagnetic object cloak. Nevertheless, we show how it is possible to use intensity-dependent refractive indices to construct an approximate STC, an implementation that would enable the distinct signature of successful event cloaking to be observed. Potential demonstrations include systems that apparently violate quantum statistics, 'interrupt-without-interrupt' computation on convergent data channels and the illusion of a Star Trek transporter.

• Open/close A completely covariant approach to transformation optics

  Robert T Thompson et al 2011 J. Opt. 13 024008 Tag this article

  Article References Full text PDF (205 KB)

  We show that the Plebanski based approach to transformation optics overlooks some subtleties in the electrodynamics of moving dielectrics that restricts its applicability to a certain class of transformations. An alternative, completely covariant, approach is developed that is more generally applicable and provides a clearer picture of transformation optics.

• Open/close Transformation optics

  Vladimir M Shalaev and John Pendry 2011 J. Opt. 13 020201 Tag this article

  Article References Full text PDF (31 KB)

  Metamaterials are artificial materials with versatile properties that can be tailored to fit almost any practical need and thus go well beyond what can be obtained with `natural' materials. Recent progress in developing optical metamaterials allows unprecedented extreme control over the flow of light at both the nano- and macroscopic scales. The innovative field of transformation optics, which is enabled by metamaterials, inspired researchers to take a fresh look at the very foundations of optics and helped to create a new paradigm for the science of light. Similar to general relativity, where time and space are curved, transformation optics shows that the space for light can also be bent in an almost arbitrary way. Most importantly, the optical space can be designed and engineered, opening up the fascinating possibility of controlling the flow of light with nanometer spatial precision. This new paradigm enables a number of novel optical devices guiding how, using metamaterials, the space for light can be curved in a pre-designed and well-controlled way.

  Metamaterials which incorporate the innovative theories of transformation optics are pertinent to the important areas of optical cloaking, optical black holes, super-resolution imaging, and other sci-fi-like devices. One such exciting device is an electromagnetic cloak that can bend light around itself, similar to the flow of water around a stone, making invisible both the cloak and the object hidden inside. Another important application is a flat hyperlens that can magnify the nanometer-scale features of an object that cannot be resolved with conventional optics. This could revolutionize the field of optical imaging, for instance, because such a meta-lens could become a standard add-on tool for microscopes. By enabling nanoscale resolution in optical microscopy, metamaterial-based transformation optics could allow one to literally see extremely small objects with the eye, including biological cells, viruses, and possibly even DNA molecules. Light-concentrating devices, such as the optical black hole, can be used for efficient solar light collection in photovoltaic elements for renewable energy.

  With the dramatic advances in micro- and nanofabrication methods, we are presented with the opportunity to control light in a way that was not possible with the materials provided to us by nature. In an artificial pattern of sub-wavelength elements, the propagation of electromagnetic energy can be defined by an equivalent spatial and spectral dispersion of effective dielectric and magnetic properties. These synthetic structures, which can be fabricated with a desired spatial distribution of effective permittivity (r) and permeability μ(r), offer a unique potential to guide and control the flow of electromagnetic energy in such an engineered optical space. No longer are we constrained by the electromagnetic response of natural materials and their chemical compounds. Instead, we can tailor the shape and size of the structural units of the metamaterials, or tune their composition and morphology to provide new functionality.

• Open/close Optical fibre nanowires and microwires: a review

  G Brambilla 2010 J. Opt. 12 043001 Tag this article

  Article References Full text PDF (1.42 MB)

  Optical fibre nanowires and microwires offer a variety of enabling properties, including large evanescent fields, flexibility, configurability, high confinement, robustness and compactness. These distinctive features have been exploited in a wealth of applications ranging from telecommunication devices to sensors, from optical manipulation to high Q resonators. In this paper I will review the fundamentals and applications of nanowires and microwires manufactured from optical fibres.

• Open/close Manipulating sources using transformation optics with 'folded geometry'

  Yun Lai et al 2011 J. Opt. 13 024009 Tag this article

  Article References Full text PDF (1.72 MB)

  Using the idea of transformation optics, we propose a way to annihilate or re-shape the radiation field of a source through remote manipulation. The manipulation is enabled by metamaterials that correspond to space folding coordinate transformations. It is shown that when two coherent sources with equal magnitudes and opposite phases are placed at equivalent positions in normal and folded spaces, they 'annihilate' each other optically. The folded space also gives the possibility of creating complex multipole sources by placing simple sources separately in normal and folded spaces. These ideas may find applications in areas such as active noise control and antenna design techniques.

• Open/close iTweezers: optical micromanipulation controlled by an Apple iPad

  R W Bowman et al 2011 J. Opt. 13 044002 Tag this article

  Article References Full text PDF (553 KB)

  The 3D interactive manipulation of multiple particles with holographic optical tweezers is often hampered by the control system. We use a multi-touch interface implemented on an Apple iPad to overcome many of the limitations of mouse-based control, and demonstrate an elegant and intuitive interface to multi-particle manipulation. This interface connects to the tweezers system hardware over a wireless network, allowing it to function as a remote monitor and control device.

• Open/close Slow light enhanced nonlinear optics in periodic structures

  C Monat et al 2010 J. Opt. 12 104003 Tag this article

  Article References Full text PDF (1.43 MB)

  We review recent advances related to slow light in periodic structures, where the refractive index varies along one or two directions, i.e. gratings and planar photonic crystals. We focus on how these geometries are conducive to enhancing the nonlinear interaction between light and matter. We describe the underlying theory developed for shallow gratings, but whose conclusions can be extended to planar photonic crystal waveguides, in particular the enhancement of third-order nonlinear processes with slow light. We review some experiments showing how gratings have been used for pulse compression and the generation of slow gap solitons. We then present recent nonlinear experiments performed in photonic crystal waveguides that demonstrate the strong reinforcement of nonlinear third-order optical phenomena with slow light. We discuss the challenges associated with slow light in these 2D structures and their unique advantage—dispersion engineering—for creating broadband nonlinear devices for all-optical signal processing. By breaking down the relation between dispersion and group velocity imposed in gratings, these structures also offer new opportunities for generating soliton-like effects over short length scales, at low powers and with short pulses.

• Open/close Transformation optics on a silicon platform

  Lucas H Gabrielli and Michal Lipson 2011 J. Opt. 13 024010 Tag this article

  Article References Full text PDF (890 KB)

  Transformation optics allows the creation of innovative devices; however, its implementation in the optical domain remains challenging. We describe here our process to design and fabricate such devices using silicon as a platform for broad band operation in the optical domain. We discuss the approximations and methods employed to overcome the challenges of using dielectric materials as a platform for transformation optics, such as the anisotropy and gradient refractive index implementation. These encompass conformal and quasi-conformal mappings, and a dithering process to discretize and quantize the continuously inhomogeneous index function. We show examples of devices that we fabricated and tested, including the carpet invisibility cloak, a broad bandwidth light concentrator, and a perfect imaging device, known as Maxwell's fish eye lens. Finally, we touch on future directions under investigation to further develop transformation optics based on dielectric materials.

• Open/close Spin-to-orbital conversion of the angular momentum of light and its classical and quantum applications

  Lorenzo Marrucci et al 2011 J. Opt. 13 064001 Tag this article

  Article References Full text PDF (1.95 MB)

  A few years ago the possibility of coupling and inter-converting the spin and orbital angular momentum (SAM and OAM) of paraxial light beams in inhomogeneous anisotropic media was demonstrated. An important case is provided by waveplates having a singular transverse pattern of the birefringent optical axis, with a topological singularity of charge q at the plate center, hence named ' q-plates'. The introduction of q-plates has given rise in recent years to a number of new results and to significant progress in the field of orbital angular momentum of light. Particularly promising are the quantum photonic applications, because the polarization control of OAM allows the transfer of quantum information from the SAM qubit space to an OAM subspace of a photon and vice versa. In this paper, we review the development of the q-plate idea and some of the most significant results that have originated from it, and we will briefly touch on many other related findings concerning the interaction of the SAM and OAM of light.

• Open/close Realization of curved Bessel beams: propagation around obstructions

  J E Morris et al 2010 J. Opt. 12 124002 Tag this article

  Article References Full text PDF (298 KB)

  We present an experimental realization of spiraling and snaking zero-order Bessel beams; light modes designed to deviate from straight-line propagation. We show that these modes can be generated with a tunable lateral deviation, amplitude and axial periodicity using a dynamic adaptive optical element, namely a spatial light modulator. We demonstrate that such beams can elude obstructions placed on the optical axis. We discuss their applications for micromanipulation and within lab-on-a-chip systems.